全新java初学者实践教程6(Java SE5.0版)
1~`fVg 基本语法3
:zbQD8jv Hqx-~hQO KYhw OGN 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
b<ZIWfs PO^ij2eS [font="Times] 1.循环语句[font="Times]:while,do-while,for
'<xXK@=KEI "ycJ:Xv49 [font="Times]2.分支语句[font="Times]:if-else,switch,
P%VSAh\|n [font="Times]
({)+3]x 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
mb3"U"ohs [font="Times]
4Uo&d#o)C- 4.异常处理语句[font="Times]:try-catch-finally,throw
W:nef<WH On.{!:"I/ 实践:
rJTa [font="Times] 1.循环语句
q5+4S5R*^ [font="Times] while 语句
$dC?Tl|B0 [font="Times]class While {
EU;9*W< [font="Times]public static void main(String args[]) {
>dD@j:Qc [font="Times]int n = 10;
1{.|+S Z! [font="Times]while(n > 0) {
70nqD>M4 [font="Times]System.out.println("tick " + n);
GPudaF{ [font="Times]n--;
]Sz:|%JP1 [font="Times]}
e}7lBLK]* [font="Times]}
n\'4 [font="Times]}
yYYSeH [font="Times] do…while 语句
EGS)b [font="Times] class DoWhile {
(gU!=F?#m [font="Times]public static void main(String args[]) {
)m)-o4c [font="Times]int n = 10;
xml7Uarc [font="Times]do {
|F[+k e [font="Times]System.out.println("tick " + n);
KqJs?Won [font="Times]n--;
50wulGJud [font="Times]} while(n > 0);
9>/4W. [font="Times]}
iC~^)-~H=w [font="Times]}
9T9!kb 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
5PJhEB [font="Times] for语句
}C?'BRX [font="Times] class ForTick {
4f@rv^f(X [font="Times]public static void main(String args[]) {
WDD%Q8ejV& [font="Times]int n;
itP,\k7>d [font="Times]for(n=10; n>0; n--)
=BAr .m+" [font="Times]System.out.println("tick " + n);
_8J.fT$${ [font="Times]}
$GcqBg-Hi [font="Times]}
HM1Fz\Sf 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
q~o<*W 还有啊,[font="Times]for循环的部分可以为空的
:\c ^*K(9 [font="Times]class ForVar {
m?}6)\ob [font="Times]public static void main(String args[]) {
p27~>xQ [font="Times]int i;
P|E| $)m [font="Times]boolean done = false;
rJ4S%6w [font="Times]i = 0;
FVbb2Y?R [font="Times]for( ; !done; ) {
f~R(D0@ [font="Times]System.out.println("i is " + i);
R+z2}}Z!` [font="Times]if(i == 10) done = true;
Y\P8v [font="Times]i++;
#p&qUw [font="Times]}
7Q9 w?y~c [font="Times]}
[l??A3G [font="Times]}
循环语句的例子下载 9;u@q%;!k [font="Times] 2.分支语句[font="Times]
?e4YGOe. [font="Times] if/else语句
-@2iaQ(5a2 [font="Times]class IfElse {
ltSU fI [font="Times]public static void main(String args[]) {
k]|~>9eY] [font="Times]int month = 4; // April
$8h%a
8I [font="Times]String season;
o5PO=AN [font="Times]if(month == 12 || month == 1 || month == 2)
9Q.Yl&A [font="Times]season = "Winter";
vn8aFA [font="Times]else if(month == 3 || month == 4 || month == 5)
my1@41
H [font="Times]season = "Spring";
l|[N42+ [font="Times]else if(month == 6 || month == 7 || month == 8)
*:7rdzn [font="Times]season = "Summer";
v!-pSa)3 [font="Times]else if(month == 9 || month == 10 || month == 11)
qYQl,w [font="Times]season = "Autumn";
!9e=_mY [font="Times]else
~G&dqw/.-U [font="Times]season = "Bogus Month";
h,N?Ab'S [font="Times]System.out.println("April is in the " + season + ".");
i1d'nxk6 [font="Times]}
EME|k{W [font="Times]}
;JT-kw6l5K [font="Times]//这段程序输出[font="Times]:
`$9x 1dx [font="Times]//April is in the Spring.
a58H9w"u) [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
qInR1 r< [font="Times] switch语句
9W5lSX#^; [font="Times] class Switch {
*N<]Xy@ [font="Times]public static void main(String args[]) {
,ZNq,$j [font="Times]int month = 4;
V f&zL
Sgr [font="Times]String season;
"HIRTE;& [font="Times]switch (month) {
s ll\g [font="Times]case 12:
PFjL1=7I [font="Times]case 1:
9$w.9`Py [font="Times]case 2:
qe#tj/aZ [font="Times]season = "Winter";
0[(8 [font="Times]break;
? OM!+O [font="Times]case 3:
1CZgb [font="Times]case 4:
<'oQ \eB [font="Times]case 5:
6d}lw6L [font="Times]season = "Spring";
F)QDJE0 [font="Times]break;
]_gU#,8
[font="Times]case 6:
q3!bky\ [font="Times]case 7:
@S;'@VC [font="Times]case 8:
/,yd+wcW# [font="Times]season = "Summer";
mq.`X:e [font="Times]break;
C<tl/NC [font="Times]case 9:
dZ@63a>>@ [font="Times]case 10:
J/$&NWF [font="Times]case 11:
f8dB-FlMm [font="Times]season = "Autumn";
&p@O_0nF [font="Times]break;
6nvz8f3*r] [font="Times]default:
Yj49t_$b [font="Times]season = "Bogus Month";
qy TU8Wp [font="Times]}
p6V0`5@t [font="Times]System.out.println("April is in the " + season + ".");
$6 f3F?y7 [font="Times]}
^ZcGY+/~ [font="Times]}
分支语句代码下载 {!L~@r /([kh~a [font="Times]switch语句适合于条件非常多的逻辑
;)*eo_tQ 请看上述语句可以混合使用,请看
下载例子